The present novel concept broadly relates to the art of vehicle suspension systems and, more particularly, to an air spring assembly having multiple load transmission paths.
In known suspension systems, particularly those utilizing spring over damper assemblies, the suspension components are often supported using a mounting arrangement that provides only a single load transmission path. It is well understood that various inputs, loads or forces are commonly associated with vehicle suspensions, including spring and jounce bumper loads which are generally unidirectional and damper loads which are normally bidirectional. Single load path mounting arrangements typically include a bearing element mounted on or within an elastomeric isolator that is secured on a mounting plate. In turn, the mounting plate is attached to the vehicle chassis or body and the loads are transmitted along the single load path through the mounting plate to the vehicle chassis or body. As a result, such single load path mounting arrangements have numerous problems and disadvantages that it is desirable to avoid.
One such disadvantage is that the elastomeric isolator must be designed to isolate the three primary suspension inputs (spring, damper and jounce bumper inputs), which commonly have significantly different magnitudes, frequencies and can also operate in different directions, as indicated above. For example, it is well understood that the spring and bumper inputs can be substantially greater than the damper inputs, and can, in some cases, exceed the damper inputs by one or more orders of magnitude. Thus, the elastomeric isolator is normally designed to at least partially reduce the transmission of all three inputs. This generally results in a compromise design that is different than the design would be for any one individual input. Unfortunately, the resulting isolator is typically biased away from a high compliance and toward a high stiffness to accommodate the higher loads of the spring and bumper inputs, and to support the entire weight of the vehicle as well. This results in increased harshness of the ride quality of the vehicle and can contribute to a corresponding decrease in passenger comfort.
Another disadvantage of such single load path mounting arrangements is that the forces of higher magnitude that are applied to the isolator tend to accelerate the degradation of the elastomeric material. As such, it is possible for undesirable characteristics, such as reduced performance of the suspension system, increased component wear and/or increased maintenance and repair costs to result from utilizing such mounting arrangements. Therefore, elastomeric isolators are often made more robust to counteract this potential change in performance, which tends to further stiffen the isolator and undesirably add to ride harshness.
In an effort to overcome these and other disadvantages, mounting arrangements have been developed that provide multiple load transmission paths for vehicle suspension inputs. However, such known arrangements are primarily used in association with steel coil springs. Those of skill in the art will recognize that in these multiple path mounting arrangements, the spring and damping member typically move independently of one another. In suspension systems that utilize coil springs, this does not normally present an issue. However, establishing and reliably maintaining a fluid-tight seal between suspension components that are capable of independent movement is considerably more challenging and can result in the generation of leak paths, component wear and other undesirable performance problems and/or losses. As such, suspension systems using air springs have heretofore been relegated to the use of single load path mounting arrangements in which the air spring and damper move in relative unison with one another and such losses and other disadvantages are more easily overcome.